High wattage lamps are used in television and movie studios to light large areas with high quality white light. These lamps typically range from 500 to 10,000 watts, and commonly have the general form of an incandescent source captured in a single ended press seal tube. A ceramic base holds the tube, and two pins that are used for the electrical connection. High wattage lamps run very hot, so a base with a high thermal resistance is needed. The bases are therefore commonly formed from a molded ceramic. The lamps also have very high power inputs, and so require oversized electrical connectors. For example, a 10,000 watt DTY studio lamp may carry as much as 88 amperes. The common electrical connectors are a pair of pins in the form of short, thick, parallel shafts. These pins may be a centimeter or greater in diameter, three centimeters or more long, and separated center to center by four or more centimeters. When positioned in a base the pins may be bolted in place by clamps that tightly bind the base connector to the pin shafts. Bolting the lamp in place assures a solid electrical connection. In actual practice lamps are repeatedly checked, adjusted or moved from site to site during or between filming sessions. The lamp pins are then repeatedly clamped and unclamped in place. In summary, the pins are necessarily sturdy shafts to endure the heat, electrical and mechanical forces placed on them. The lamp pins are commonly machined from solid stock, but machined pins are both heavy, and expensive. There is then a need for a less expensive and lighter weight pin.
Extruded hollow pins have been used, but have been found at times to cause arcing between the pin and base connector in the confines of the base. The hollow pins are at times heated, burned, pitted, or partially melted by the arcing currents. The arcing may cause the lamps to fail prematurely, and naturally causes safety concerns in the user. There is then a need for a pin that does not cause base arcing, and the associated pin destruction.
Examples of the prior art are shown in U.S. Pat. Nos, 4,084,112; 4,492,814; 4,499,404; 4,758,760; 4,766,347; and 4,785,218.
U.S. Pat. No. 4,084,112 Herbert et al. shows a pin lamp having hollow lamp pins. The hollow pins are flattened at the internal ends to allow a welded contact to be made with the lamp connection, and to position the pins in the ceramic base.
U.S. Pat. No. 4,492,814 Snell et. al shows a press sealed lamp having a cavity formed around the lamp connection on the exterior side of the sealing foil. The cavity is then filled with a solder glass to prevent oxidation of the lamp lead, and the foil seal.
U.S. Pat. No. 4,499,404 Walsh shows a pin lamp having a two piece ceramic base. The lamp is cemented in the upper portion of the ceramic base, and the lamp connections are extended down to metal pins captured in the lower portion of the ceramic base. While there is no discussion of the pin structure, the lamp shown is thought to be an example of studio lamps with machined pins.
U.S. Pat. No. 4,758,760 Cox et al shows a ceramic base with a main cavity to hold a lamp, ventilated connection passages that enclose the lamp seal legs, and pin cavities that position and hold two pins for electrical connection. U.S. Pat. No. 4,758,760 shows substantially the preferred embodiment of the remaining lamp and base portions as used by the applicants. A different lamp leg structure is shown in U.S. Pat. No. 4,758,760 than is preferred by the applicants here. U.S. Pat. No. 4,758,760 is therefore incorporated by reference for purposes of generally instructing the structure of the lamp and lamp base.
U.S. Pat. No. 4,766,347 Janssen et. al shows a high pressure discharge lamp wherein a glass material is melted around the lamp connection to seal the connection to an adjacent mounting element.
U.S. Pat. No. 4,785,218 Kohl et al. shows a pin lamp with hollow lamp pins. The lamp connections are threaded through the hollow lamp pins, and then solder is used to fill the remaining volume of the lamp pin cavity. The solder completes the connection between the lamp connections and the base pins. While solder may be used to fill the cavity of a small pin, the solder being mostly lead would excessively weight a large lamp. Furthermore, solder is neither mechanically strong, or resistant to high heat or electric currents. A solder plug in a high wattage lamp might melt, sag, or otherwise fail under the mechanical or heat load.